Guilding introducer system for use in the left atrium

ABSTRACT

A guiding introducer system for use in the left atrium comprised of an inner guiding introducer and an outer guiding introducer wherein the inner guiding introducer is comprised of a first and second section and the outer guiding introducer is comprised of a first and second sections. The guiding introducer system is for use in sensing, pacing, and ablating procedures within the left atrium of the human heart.

This application is a division of Ser. No. 08/333,791 filed Nov. 3,1994, now U.S. Pat. No. 5,564,440, which was a continuation-in-partapplication of Ser. No. 08/147,168 filed Nov. 3, 1993, now U.S. Pat. No.5,497,774.

BACKGROUND OF INVENTION

1. Field of Invention

This invention relates to introducers. More particularly, this inventionrelates to a guiding introducer system for use within the left atrium ofthe human heart.

2. Prior Art

Introducers and catheters have been in use for medical procedures formany years. For example, one use has been to convey an electricalstimulus to a selected location within the human body. Another use isthe monitoring of measurements for diagnostic tests within the humanbody. Thus, catheters may be used by a physician to examine, diagnoseand treat while positioned at a specific location within the body whichare otherwise inaccessible without more invasive procedures. Cathetersmay be inserted into a major vein or artery which is near the bodysurface. The catheters are then guided to the specific location forexamination, diagnosis or treatment by manipulating the catheter throughthe artery or vein of the human body.

Catheters have become increasingly useful in remote and difficult toreach locations within the body. However, the utilization of thesecatheters is frequently limited because of the need for the preciseplacement of the tip of the catheter at a specific location within thebody.

Control of the movement of catheters to achieve such precise placementis difficult because of the inherent structure of a catheter. The bodyof a conventional catheter is long and tubular. To provide sufficientcontrol of the movement of the catheter, it is necessary that itsstructure be somewhat rigid. However, the catheter must not be so rigidas to prevent the bending or curving necessary for movement through thevein, artery or other body part to arrive at the specified location.Further, the catheter must not be so rigid as to cause damage to theartery, vein or body part while it is being moved within the body.

While it is important that the catheter not be so rigid as to causeinjury, it is also important that there be sufficient rigidity in thecatheter to accommodate torque control, i.e., the ability to transmit atwisting force along the length of the catheter. Sufficient torquecontrol enables controlled maneuverability of the catheter by theapplication of a twisting force at the proximal end of the catheter thatis transmitted along the catheter to its distal end. The need forgreater torque control often conflicts with the need for reducedrigidity to prevent injury to the body vessel.

Catheters are used increasingly for medical procedures involving thehuman heart. In these procedures a catheter is typically advanced to theheart through veins or arteries and then is positioned at a specifiedlocation within the heart. Typically, the catheter is inserted in anartery or vein in the leg, neck, upper chest or arm of the patient andthreaded, often with the aid of a guidewire or introducer, throughvarious arteries or veins until the tip of the catheter reaches thedesired location in the heart.

The distal end of a catheter used in such a procedure is sometimespreformed into a desired curvature so that by torquing the catheterabout its longitudinal axis, the catheter can be manipulated to adesired location within the heart or in the arteries or veins associatedwith the heart. For example, U.S. Pat. No. 4,882,777 discloses acatheter with a complex curvature at its distal end for use in aspecific procedure in the right ventricle of a human heart. U.S. Pat.No. 5,231,994 discloses a guide catheter for guiding a balloon catheterfor the dilation of coronary arteries. U.S. Pat. No. 4,117,836 disclosesa catheter for the selective coronary angiography of the left coronaryartery and U.S. Pat. Nos. 5,299,574, 5,215,540, 5,016,640 and 4,883,058disclose catheters for use in selective coronary angiography of theright coronary artery. See also U.S. Pat. No. 4,033,031. Finally, U.S.Pat. No. 4,898,591 discusses a catheter with inner and outer layerscontaining braided portions. The '591 patent also discloses a number ofdifferent curvatures for intravascular catheters.

In addition to single catheters with various curvatures, U.S. Pat. No.4,581,017 discloses an inner and outer guide catheter, (numbers 138 and132), for use with a balloon catheter for treatment of coronaryarteries. U.S. Pat. No. 5,267,982 discloses a catheter assembly andmethods for catheterization of coronary arteries wherein an innercatheter (50) and outer catheter (52) are used in combination for thetreatment of right and left coronary angiographic procedures. See alsoU.S. Pat. No. 4,935,017 which discloses a similar device. U.S. Pat. No.5,290,229 discloses a straight outer sheath and a preformed innercatheter for use in the heart. See also U.S. Pat. Nos. 5,304,131,5,120,323, 4,810,244 and 5,279,546.

Thus, there are a number of patents which disclose catheters withpredetermined shapes, designed for use in specific medical proceduresgenerally associated with the heart or the vascular system. Because ofthe precise physiology of the heart and the vascular system, cathetersor introducers with carefully designed shapes for predetermined useswithin the human heart and vascular system are important.

The sources of energy used for catheter ablation vary. Initially, highvoltage, direct current (DC) ablation techniques were commonly used.However, because of problems associated with the use of DC current,radio frequency (R.F.) ablation has become a preferred source of energyfor the ablation procedures. The use of RF energy for ablation has beendisclosed, for example, in U.S. Pat. Nos. 4,945,912, 5,209,229,5,281,218, 5,242,441, 5,246,438, 5,281,213 and 5,293,868. Other energysources being considered for ablation of heart tissue include laser,ultrasound, microwave and direct current fulgutronization procedures.Also disclosed have been procedures where the temperature about thecatherization probe is modified.

Catheter ablation of accessory pathways associated withWolfe-Parkinson-White syndrome using a long vascular sheath by both atransseptal and retrograde approach is discussed in Saul, J. P., et al."Catheter Ablation of accessory Atrioventricular Pathways in YoungPatients: Use of long vascular sheaths, the transseptal approach and aretrograde left posterior parallel approach" Journal of the AmericanCollege of Cardiology, Vol. 21, no. 3, pps. 571-583 (Mar. 1, 1993). Seealso Swartz, J. F. "Radiofrequency Endocardial Catheter Ablation ofAccessory Atrioventricular Pathway Atrial Insertion Sites" Circulation,Vol. 87, no. 2, pps. 487-499 (February, 1993).

Accordingly, it is an object of this invention to prepare a dual guidingintroducer system for selected medical procedures in the left atrium.

It is a further object of this invention to prepare a dual guidingintroducer system for use in selected electrophysiology procedureswithin the left atrium of the heart.

Another object of this invention is to prepare a dual guiding introducersystem for use in selected ablation procedures within the left atrium ofthe heart.

These and other objects are obtained by the design of the guidingintroducer system disclosed in the instant invention.

SUMMARY OF INVENTION

The instant invention is a guiding introducer system for selectedmedical procedures in the left atrium. It is comprised of an innerguiding introducer and an outer guiding introducer. A dilator ispreferably used with the guiding introducer system, which dilator may bea transseptal dilator used with a Brockenbrough needle. The innerguiding introducer is a shaped introducer comprised of a first andsecond section, wherein the first section is a generally elongatedstraight section which is merged at its distal end with the secondsection which is a simple curved section. The outer guiding introduceris comprised of a first and second sections, wherein the first sectionis a generally elongated straight section which is merged at its distalend with the second section which forms a complex curved section. Theinner guiding introducer is longer than the outer guiding introducer topermit it to extend out from the lumen of the outer guiding introducerto form various curves and shapes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of the left side of the heart showing themitral valve and the placement of the guiding introducer system.

FIG. 2 is a perspective view of the preferred dilator.

FIG. 3 is a perspective view of the inner guiding introducer.

FIG. 4 is a perspective view of the outer guiding introducer.

FIG. 5 is a perspective view of the inner and outer guiding introducersin combination with the distal end of the inner guiding introducerextended from the distal end of the outer guiding introducer.

DETAILED DESCRIPTION OF THE DRAWINGS

A typical human heart includes a right ventricle, a right atrium, leftventricle and left atrium. The right atrium is in fluid communicationwith the superior vena cava and the inferior vena cava. Theatrioventricular septum separates the right atrium from the rightventricle. The tricuspid valve contained within the atrioventricularseptum communicates the right atrium with the right ventricle. On theinner wall of the right atrium where it is connected with the leftatrium is a recessed portion, the fossa ovalis. See FIG. 1. In the heartof a fetus, the fossa ovalis is open, permitting the fetal blood to flowbetween the right and left atria. In most individuals, this openingcloses after birth, but in as many as 25 percent of individuals anopening still remains in the fossa ovalis between the right and leftatria. Between the fossa ovalis and the tricuspid valve is the openingor ostium for the coronary sinus. The coronary sinus is the largeepicardial vein which accommodates most of the venous blood which drainsfrom the myocardium into the right atrium.

In the normal heart, contraction and relaxation of the heart muscle(myocardium) takes place in an organized fashion as electrochemicalsignals pass sequentially through the myocardium from the atrial to theventricular tissue along a well defined route which includes theHis-Purkinje system. Initial electrical impulses are generated at thesinuatrial (SA) node and conducted to the atrioventricular (AV) node.The AV node lies near the ostium of the coronary sinus in theinteratrial septum in the right atrium. The His-Purkinje system beginsat the AV node and follows along the membranous interatrial septumtoward the tricuspid valve through the atrioventricular septum and intothe membranous interventricular septum. At about the middle of theinterventricular septum, the His-Purkinje system splits into right andleft branches which straddle the summit of the muscular part of theinterventricular septum.

Sometimes abnormal rhythms occur in the heart which are referred to asarrhythmia. For example, a common arrhythmia is Wolfe-Parkinson-Whitesyndrome (W-P-W). The cause of W-P-W is generally believed to be theexistence of an anomalous conduction pathway or pathways that connectsthe atrial muscle tissue directly to the ventricular muscle tissue, thusby-passing the normal His-Purkinje system. These pathways are usuallylocated in the fibrous tissue that connects the atrium and theventricle. In recent years a technique has been developed to destroythese anomalous conduction pathways by delivering energy into the tissuein which the pathways exist. To accomplish this procedure a specialelectrode catheter is positioned as close as possible to the anomalousconduction pathway to maintain constant tissue contact while energy isdelivered to the cardiac tissue to destroy the pathway. This same typeof contact with the cardiac tissue is also necessary when mapping orother such procedures are employed relating to these pathways.

One end of these anomalous conduction pathways can be located either inthe right atrium or in the left atrium with the other end of the pathwaylocated in the corresponding ventricle. When the anomalous conductionpathway is located between the left atrium and the left ventricle, thereare two approaches to positioning the catheter near the pathway for theappropriate medical procedure. One is to introduce the catheter into thefemoral artery by a standard introducer sheath and advance it up theaorta, across the aortic valve into the left ventricle and then attemptto position its tip under the mitral valve annulus near the anomalousconduction pathway. This approach is frequently difficult for manyreasons, including the structure of the left ventricle, the fact that itrequires arterial access and potential problems associated with ablationof ventricular tissue such as the creation of a substrate for a futurearrhythmia which could result in sudden cardiac death. The otherapproach is to introduce a transseptal sheath apparatus, a long singleplane curve introducer, into the right femoral vein and advance itthrough the inferior vena cava into the right atrium. A puncture is thenmade through the fossa ovalis in the interatrial septum and theapparatus is advanced into the left atrium where the trocar and dilatorof the apparatus are removed, leaving the introducer in position in theleft atrium. The mapping or ablation catheter is then inserted throughthe introducer and into the left atrium and positioned on top of themitral valve annulus near the anomalous conduction pathway. Specificpositions may be chosen for the mapping or ablation on the left side ofthe heart, including specifically posteroseptal, posterior,posterolateral, lateral and anterolateral positions around the mitralvalve annulus.

Traditionally, there have been two techniques for locating and ablatinganomalous conduction pathways which are situated between the rightatrium and right ventricle. Either method can be initiated by advancinga catheter through an access site into a vein in the leg, neck or upperchest.

The first technique, which approaches the pathway from the pathway'sventricular insertion site, involves entering the right atrium fromeither the inferior or superior vena cava, passing through the tricuspidvalve, and advancing toward the apex of the right ventricle. Then thecatheter is directed to make a 180 degree turn to reverse its path backup toward the right atrium and locate the accessory pathway under thetricuspid valve apparatus. The accessory pathway is then ablated fromthe ventricular insertion site under the tricuspid valve.

The second technique, which approaches the pathway from the atrialinsertion site, is to enter the right atrium from the inferior orsuperior vena cava, and attempt to locate the atrial insertion site ofthe accessory pathway around the tricuspid valve annulus. The accessorypathway is then ablated from the pathway's atrial insertion site on theatrial aspect of the tricuspid valve.

AV nodal pathways can be located and ablated from the right atrium.

Mere introduction of the catheter into the left atrium is not sufficientto effectively and efficiently perform these medical procedures,especially the mapping or ablation of anomalous conduction pathways.These medical procedures are usually performed using a specificcatheter. The medical practitioners monitor the introduction of thecatheter and its progress through the vascular system by a fluoroscope.However, such fluoroscopes do not easily identify the specific featuresof the heart in general and the critically important structures of theleft atrium in specific, thus making placement of the catheterdifficult. This placement is especially difficult as the beating heartis in motion and the catheter will be moving within the left atrium asblood is being pumped through the heart throughout the procedure. Thestructure and shape of the guiding introducer of the instant inventionaddresses and solves these problems.

The guiding introducer system for use in the left atrium is comprised ofan inner and an outer guiding introducer. See FIG. 5. A dilator is alsopreferably used wherein the dilator may be a transseptal dilator usedwith cardiac procedures requiring a Brockenbrough needle for atransseptal puncture and is generally curved. See FIG. 2. Generally thedistal end is curved in a curve with a radius of about 3.0 to 4.0 in.with an arc of about 20 to about 40 degrees ending in a conventionaldistal tip. The standard length of the dilator is about 60 to about 80cm. Alternatively, a different dilator may be used without aBrockenbrough needle.

The inner guiding introducer is generally comprised of two sections. SeeFIG. 3. The first section is a conventional generally elongated hollowstraight catheter section of sufficient length for introduction into thepatient and for manipulation from the point of insertion to the specificdesired location within the heart. Merged with the distal end of thefirst section of the guiding introducer, but an integral part of theentire guiding introducer, is the second section which is a curvedsection, curved in a simple curve with a radius of about 0.5 to about2.0 in., preferably about 0.7 to about 1.3 in. to form an arc ofapproximately 150 to about 270 degrees, preferably about 170 to about190 degrees ending in a distal tip.

The outer guiding introducer for use in the left atrium is comprised ofa first and second sections. See FIG. 4. (As with the inner guidingintroducer, this division into two separate sections is for ease ofillustration. The guiding introducer is preferably formed in a singleprocedure with each section an integral part of the overall guidingintroducer.) The first section is a conventional, generally elongatedhollow straight catheter section of sufficient length for introductioninto the patient and for manipulation from the point of insertion to thespecific desired location within the heart. Merged with the distal endof the first section of the guiding introducer is the second sectionwhich is comprised of a compound curved section curving both upward andto the right (as shown in FIG. 4). This curved section first curvesupward in a curve with a radius of about 0.3 to about 0.7 in. with anarc of approximately 40 to about 60 degrees, preferably about 45 toabout 55 degrees. At the same time as the curved section curves upward,it also curves to the right in a simple curve with a radius of fromabout 0.70 to about 1.30 in. and preferably from about 0.80 to about1.20 in. with an arc of about 30 degrees to about 60 degrees, andpreferably from about 40 degrees to about 50 degrees, ending in thedistal tip of the outer guiding introducer.

By extending the distal tip of the inner guiding introducer away fromthe distal tip of the outer guiding introducer and by rotating the innerguiding introducer with respect to the outer guiding introducer, avariety of shapes of the overall guiding introducer system are formed todirect the mapping and/or ablation catheter toward the site within theatrium of interest. See FIG. 5. These shapes permit ablation procedureswithin the left atrium to be performed, for example, around the mitralvalve annulus in various positions such as anterior to anterolateral tolateral to posterolateral to posteroseptal to septal. The variouslocations can be treated by extending the inner guiding introducerfurther from the outer guiding introducer which forms a differentoverall shape and/or by rotating the inner guiding introducer withrespect to the outer guiding introducer. In addition, by manipulation ofthe inner guiding introducer within the outer guiding introducer,additional procedures can be performed within the left atrium, forexample, for treatment of ectopic atrial tachycardia or even for certainatrial fibrillation procedures. Being able to extend the inner guidingintroducer within the outer guiding introducer and to rotate the innerguiding introducer within the outer guiding introducer permits a widevariety of overall shapes, which is particularly useful to the medicalpractitioners. The medical practitioner is able to determine therelative location of the inner and outer guiding introducers because oftip markers located near the distal tip of both the inner and outerguiding introducers.

The distal tip of both the inner and outer guiding introducers may be,and generally will be, tapered to form a good transition with thedilator.

The relative size of the outer guiding introducer in relation to theinner guiding introducer should be sufficient to permit the innerguiding introducer to be torqued or rotated within the outer guidingintroducer without undue restriction on such movement. Preferably, thedifference in size between the inner and outer guiding introducer shouldbe at least about 3 "French" (1 French equals about one-third of amillimeter). For example in one preferred embodiment, the outer guidingintroducer is 11 French in size and the inner guiding introducer is 8French. By this difference in diameter, there is approximately 1 Frenchunit of volume available between the outer surface of the inner guidingintroducer and the inner surface of the outer guiding introducer.Preferably, this volume of space between the inner and outer guidingintroducer is filled with a biocompatible solution, such as a salinesolution, preferably a heparinized saline solution. This saline solutionalso provides lubricity to the two guiding introducers, allowing moreaccurate torquing of the inner guiding introducer within the outerguiding introducer. In addition, it is preferable that the structure ofboth the inner and the outer guiding introducer have a high torsionalconstant to allow for the full utilization of the various shapesavailable by rotation and extension of the inner and outer guidingintroducer. To permit this high torsional constant, in one preferredembodiment the inner guiding introducer is braided to provide furtherstrength and structural stability.

The guiding introducer may be made of any material suitable for use inhumans, which has a memory or permits distortion from and subsequentsubstantial return to the desired three dimensional or complexmulti-planar shape. For the purpose of illustration and not limitation,the internal diameter of the tip of the guiding introducers may varyfrom about 6 to about 10 "French" Such guiding introducers can acceptdilators from about 6 to about 10 French and appropriate guidewires.Obviously if larger, or smaller dilators and catheters are used inconjunction with the guiding introducers of the instant invention,modification can be made in the size of the instant guiding introducers.

The pair of guiding introducers preferably contain one or a multitude ofradiopaque tip marker bands near the distal tip of the guidingintroducers. Various modifications may be made in the shapes byincreasing or decreasing its size or adding additional tip markers.

The inner and outer guiding introducers also preferably contain one or aplurality of vents near the distal tip of the guiding introducers,preferably 3 or 4 or such vents. The vents are preferably located nomore than about 5 to 6 cm. from the tip of the guiding introducers andmore preferably 0.5 cm. to about 4.0 cm. from the tip. The size of thesevents should be in the range of about 20 to 60 1/1000 of an inch indiameter. These vents are generally designed to prevent air embolismsfrom entering the guiding introducers caused by the withdrawal of acatheter contained within the guiding introducers in the event thedistal tip of one of the guiding introducers is occluded. For example,if the tip of the inner guiding introducer is placed against themyocardium and the catheter located within the inner guiding introduceris withdrawn, a vacuum may be created within the inner guidingintroducer if no vents are provided. If such vacuum is formed, air maybe forced back into the guiding introducer by the reintroduction of acatheter into the lumen of the guiding introducers. Such air embolismcould cause problems to the patient including the possibility of astroke, heart attack or other such problems common with air embolisms inthe heart. The addition of vents near the distal tip of the guidingintroducers prevents the formation of such vacuum by permitting fluid,presumably blood, to be drawn into the lumen of the guiding introducersas the catheter is being removed, thus preventing the possibility offormation of an air embolism.

Variances in size or shape of the pair of guiding introducers are alsointended to encompass pediatric uses for the pair of guiding introducersof the instant invention, although the preferred use is for adult humanhearts. It is well recognized that pediatric uses may require reductionsin size of the various sections of the guiding introducers in particularthe first section, but without any significant modification to the shapeor curves of the guiding introducers. However, because incrementalchanges can be made in the overall shape of the pair of guidingintroducers, the system can better adjust to differing shapes and sizesof heart than can a single guiding introducer.

In operation, a modified Seldinger technique is normally used for theinsertion of a catheter into either an artery or vein of the body. Usingthis procedure, a small skin incision is made at the appropriatelocation to facilitate the catheter and dilator passage. Thesubcutaneous tissue is then dissected, followed by a puncture of thevessel with an appropriate needle with stylet positioned at a relativelyshallow angle. The needle is then partially withdrawn and reinserted ata slightly different angle into the vessel, making sure that the needleremains within the vessel. A soft flexible tip of an appropriate sizedguidewire is then inserted through and a short distance beyond theneedle into the vessel. Firmly holding the guidewire in place, theneedle is removed. The guidewire is then advanced through the vesselinto the right atrium. With the guidewire in place, the dilator is thenplaced over the guidewire with the pair of guiding introducers placedover the dilator. The dilator and pair of guiding introducers generallyform an assembly to be advanced together along the guidewire into theright atrium. After insertion of the assembly, the guidewire is thenwithdrawn. A Brockenbrough or trocar needle is then inserted through thelumen of the dilator to the right atrium to be used to create an openingthrough the interatrial septum, preferably at the fossa ovalis. The tiprests against the intraatrial septum at the level of the fossa ovalis.The Brockenbrough needle is then advanced within the dilator to reachthe fossa ovalis. After the opening is made through the interatrialseptum, the needle, dilator and pair of guiding introducers are advancedinto the left atrium. After the pair of guiding introducers are advancedthrough the interatrial septum into the left atrium, the Brockenbroughor trocar and dilator are removed, leaving the pair of guidingintroducers in the left atrium. The catheter to be used for analysisand/or treatment of the anomalous conduction pathways is then advancedthrough the lumen of the pair of guiding introducers and is placed at anappropriate location near the mitral valve annulus. By extending andwithdrawing the inner guiding introducer from the outer guidingintroducer and by rotating the inner guiding introducer within the outerguiding introducer, great variances in the overall shape of the guidingintroducer system can be achieved.

By movement of the inner guiding introducer within the outer guidingintroducer in conjunction with fluoroscopic viewing, the distal portionof the outer guiding introducer can be manipulated to direct the distalend of a catheter placed within the lumen of the inner guidingintroducer to a specific internal surface within the left atrium. SeeFIG. 5. In addition, by providing sufficient rigidity, the distal end ofthe inner guiding catheter can be maintained in that fixed location orsurface position of the endocardial structure to permit the appropriateprocedures to be performed. If sensing procedures are involved, the pairof guiding introducers are placed in the desired location. At thatpoint, the electrical activity of the heart peculiar to that locationcan be precisely determined by use of an electrophysiology catheterplaced within the guiding introducers. Further, as the pair of guidingintroducers permit precise location of catheters, an ablation cathetermay be placed at a precise location for destruction of the cardiactissue by the use of energy, for example, radio frequency, thermal,laser or direct current (high energy direct, low energy direct andfulgutronization procedures). The precise placement of the ablationcatheter tip on the cardiac tissue is important as there will be nodilution of the energy delivered due to unfocused energy beingdissipated over the entire cardiac chamber and lost in the circulatingblood by a constant movement of the tip of the ablating catheter. Thispermits a significantly reduced amount of energy to be applied, whilestill achieving efficient ablation. Further, time used to perform theprocedure is significantly reduced over procedures where no guidingintroducers are used.

It will be apparent from the foregoing that while particular forms ofthe invention have been illustrated and described, various modificationscan be made without departing from the spirit and scope of theinvention. Accordingly, it is not intended that this invention belimited except as by the appended claims.

We claim:
 1. A guiding introducer system comprised of an inner guidingintroducer containing a lumen therethrough and an outer guidingintroducer containing a lumen therethrough, wherein the inner guidingintroducer is advanced into the lumen of the outer guiding introducerand wherein said guiding introducers are used in combination, and adilator containing distal and proximal ends, wherein said dilator curvesat its distal end in a simple curve with a radius of about 3.0 to about4.0 in. with an arc of about 20 to about 40 degrees.
 2. A guidingintroducer system comprised of an inner guiding introducer and an outerguiding introducer wherein the inner guiding introducer is comprised ofa first and second sections each with proximal and distal ends, whereinthe first section is a generally elongated straight section, whereinmerged with the distal end of said first section is the second sectionwhich is a curved section with a radius of about 0.5 to about 2.0 in. toform an arc of approximately 150 to 270 degrees ending in the distal endof the second section of the inner guiding introducer.
 3. The precurved,cardiac chamber guiding introducer system of claim 2 wherein a pluralityof vents is provided near the distal end of the second section of theinner guiding introducer.
 4. The precurved, cardiac chamber guidingintroducer system of claim 2 wherein tip markers are contained withinthe inner guiding introducer.
 5. A guiding introducer system comprisedof an inner guiding introducer and an outer guiding introducer whereinthe outer guiding introducer is comprised of a first and second sectionseach with proximal and distal ends, wherein the first section is agenerally elongated straight section, wherein merged with the distal endof said first section is the second section which is comprised of acompound curved portion, curving in a curve with a radius of about 0.3to about 0.7 in. to form an arc of about 40 to about 60 degrees and atthe same time curving in a curve with a radius of about 0.8 in. to about1.2 in. to form an arc of about 30 to 60 degrees, ending in the distalend of the second section of the outer guiding introducer.
 6. Theprecurved, cardiac chamber guiding introducer system of claim 5 whereina plurality of vents is provided near the distal end of the secondsection of the outer guiding introducer.
 7. The precurved, cardiacchamber guiding introducer system of claim 5 wherein tip markers arecontained within the outer guiding introducer.